Strategies for Improving the Techno-Functional and Sensory Properties of Bean Protein

Abstract

This review aims to understand the techno-functional and structural properties of bean proteins, highlighting their strengths and weaknesses while presenting them as a robust alternative protein source with high potential to become a competitive ingredient in the protein market. For this purpose, ScienceDirect and Scopus were used as databases with the keywords “bean proteins”, “protein modifications + beans”, and “techno-functional properties + beans” to consult the relevant literature. This could reduce global dependence on soy and pea proteins. The study compiles various current articles that address desirable techno-functional properties and potential modifications for a wide range of food industry applications. Based on the gathered findings, bean-derived proteins exhibit a more hydrophobic nature and a more compact structure compared to soy and pea proteins. Consequently, they demonstrate superior emulsifying properties and an excellent oil absorption capacity, making them promising ingredients for emulsified products and baked goods. On the other hand, soy and pea proteins perform better in meat-based products and confectionery due to their higher water absorption capacity and good stability.

1. Introduction

The protein market is a rapidly expanding sector within the food industry, with an expected growth rate of 9.1% from 2020 to 2027 [1]. There has been a growing interest in the consumption of plant-based products, particularly in alternative plant proteins to meat. The number of companies focusing on plant-based products as alternatives to animal-derived products and utilizing alternative protein sources has been steadily increasing. Factors such as the rise in sustainable production, the pursuit of conscious use of green technologies, and greater attention to environmental issues drive higher productivity and market value. These factors encourage research and investment in the sector, which, in the long term, can foster the development of the alternative protein market for application in products with diverse purposes [2].

Proteins play a crucial role in human nutrition, offering health benefits while providing various techno-functional properties to foods, including emulsifying and foaming capacities [3]. Countries that consume the most plant-based protein generally include those with diets rich in legumes, grains, and vegetables. According to the FAO, countries such as India, Brazil, and China are known for their high consumption of plant-based proteins, due to their traditional cuisines that incorporate a variety of beans, lentils, and other protein-rich vegetables. The demand for these molecules has been increasing due to their wide range of applications. Globally, 80% of the protein demand is met by plant-based sources, while 20% comes from animal sources. Of the proteins consumed in the human diet, 65% are derived from plant-based foods [4].

Typically, legumes, seeds, and seaweeds serve as sources of plant-based protein. Legumes (soy, lentils, and peas), nuts (cashews, macadamia nuts, and almonds), seeds (chia and flaxseed), and pseudo-grains (quinoa and buckwheat) have been gaining prominence in the protein market as alternative sources to animal-based proteins [5].

Proteins extracted from beans have also gained prominence in the global scientific and technological landscape [6,7,8,9]. The leading global producers of beans are India, Brazil, Myanmar, Tanzania, Uganda, China, the United States, Mexico, Argentina, and Ethiopia (Figure 1) [10]. The Americas are responsible for an average annual production of 27.9% of all beans produced worldwide.

Beans are foods rich in micronutrients such as potassium, magnesium, folate, iron, and zinc, in addition to being sources of protein in diets alternative to those based on animal origin [11,12,13]. Their protein composition is based on globulins, gliadin, glutelin, and a high albumin content. However, the aroma of beans and their dark color limit their use in certain products [12]. In addition to this phenomenon, beans may contain antinutritional factors such as phytates, protease and amylase inhibitors, lectins, and polyphenols (tannins), which can reduce enzymatic activity and the absorption of certain metabolites. Furthermore, the nutritional value of the proteins is lower, as they do not contain significant levels of essential amino acids [14,15].

Due to the low functionality of bean proteins, some chemical, physical, and biological modifications are commonly employed to overcome their restricted applications in the food industry (Figure 2) [16]. The aim of this review is to present the main strategies being employed to modify bean proteins in order to improve their techno-functional characteristics, with the goal of increasing their use as ingredients in the food industry. This review also provides a discussion of the advantages and disadvantages of each strategy and the prospects for using bean proteins as substitutes for both plant-based and animal proteins in human nutrition.

Previous literature reviews address the physicochemical characteristics and properties of specific varieties of beans, as well as the application of proteins from these legumes [17,18]. Others mention the techno-functional modifications in bean proteins, but this is not the main focus of the review [8]. Furthermore, when the focus of the literature review is the techno-functional modification of bean proteins, the focus of the article is only on one technology, that of ultrasound [19]. The uniqueness of this literature review lies in its presentation of a wide range of strategies for modifying bean proteins, aiming to enhance their techno-functional properties and promote their application in food products. This article provides readers with a resource to select the appropriate methodology based on the desired characteristics of the final product, while understanding the advantages and disadvantages of each technique, thus enabling them to justify its use in scientific research.

For this purpose, ScienceDirect and Scopus were used as databases to search for relevant scientific articles from the last 10 years. The keywords used for the search were “bean proteins”, “techno-functional properties + beans”, and “protein modifications + beans”. For discussion in this review, articles that dealt with modifications of bean proteins in relation to their techno-functional and sensory characteristics were selected. In order to avoid confusion throughout the discussion, we will call “beans” the varieties of the genera Phaseolus, Vigna, Vicia, and Lablab that have common characteristics. When necessary, we will specify which variety the characteristics refer to.

2. Bean Proteins vs. Soy and Pea Proteins

2.1. Chemical Composition

Food proteins are assessed for their quality based on their ability to meet the nutritional requirements of humans through essential and non-essential amino acids, ensuring the protein synthesis necessary for all metabolic processes in the human body [20,21]. Their nutritional value is based on the composition, digestibility, bioavailability of essential amino acids, absence of toxicity, and the presence of antinutritional factors [22].

Plant-based proteins typically face two barriers regarding their nutritional value: they may lack one or more of the essential amino acids [23] and they contain antinutritional factors that can limit their digestion [24].

It is observed that all the proteins reported contain non-zero amounts of essential amino acids (

Table 1. Amino acid profile found in concentrated and/or isolated protein from beans, peas, and soy.

Amino Acid (g·100 g−1)	Bean			Pea			Soy
Alanine	5.07	3.97	3.2	4.59	5.4	3.2	4.5	2.8	4.2
Arginine *	7.01	8.96	7.2	7.98	8.4	5.9	7.8	4.8	8.0
Aspartic Acid	10.17	9.28	8.7	10.50	11.9	ND	11.8	ND	12.1
Cysteine	ND	1.26	0.5	1.54	1.0	0.2	1.2	0.2	1.4
Glutamic Acid	19.50	15.67	14.0	17.34	16.4	12.9	20.5	12.4	20.4
Glycine	3.60	3.95	3.2	4.33	4.0	2.8	4.4	2.7	4.2
Histidine *	2.48	2.61	2.0	2.94	2.4	1.6	2.5	1.5	2.7
Isoleucine *	5.47	3.67	3.4	4.25	4.4	2.3	4.9	1.9	4.3
Leucine *	9.33	6.57	6.5	6.70	7.6	5.7	5.6	5.0	7.8
Lysina *	6.82	5.97	4.7	7.20	6.7	4.7	5.6	3.4	6.5
Methionine *	1.29	0.52	0.6	0.72	0.9	0.3	1.4	0.3	1.4
Phenylalanine *	6.79	3.98	3.3	4.83	5.7	3.7	5.5	3.2	5.4
Proline	4.06	4.27	4.3	5.00	4.4	3.1	4.9	3.3	5.3
Serine	2.47	4.28	4.2	4.75	5.4	3.6	5.2	3.4	5.7
Threonine *	1.77	2.96	3.0	3.40	3.8	2.5	3.9	2.3	3.6
Tyrosine	2.99	3.16	2.5	3.37	4.0	2.6	3.9	2.2	4.1
Valine *	6.72	3.41	3.6	3.97	4.9	2.7	5.1	2.2	4.5
Tryptophan *	ND	ND	0.4	ND	0.9	ND	1.3	ND	1.0
References	[25,26]			[25,27,28]			[27,28,29]

Not determined. * Essential amino acids.

). Among the ten essential amino acids, bean proteins exhibit the highest values for five of them, pea proteins for two, and soy proteins for three. Therefore, it can be inferred that the consumption of bean proteins ensures higher values for half of the essential amino acids for human consumption. Bean proteins also contain a higher amount of non-polar and uncharged amino acids in their side chains, such as alanine, valine, leucine, isoleucine, phenylalanine, and methionine, thus exhibiting a more hydrophobic character compared to soy and pea proteins. In contrast, soy and pea proteins have a higher amount of hydrophilic and charged amino acids in their side chains, such as lysine, arginine, and glutamine, with soy > pea. The same trend is observed for amino acids with charged side chains, with soy and pea proteins having the highest amounts, respectively.

This amino acid balance plays a key role in the techno-functional properties of proteins. Since those with a higher content of hydrophobic amino acids on their surface, such as bean proteins, generally exhibit better emulsifying properties and oil absorption, they are more effective in emulsified products. In contrast, proteins with a higher content of hydrophilic amino acids, like soy and pea proteins, typically display better gelling and foaming properties. Proteins with a high content of charged amino acids can also exhibit good network stability, as electrostatic repulsion between the charges helps maintain a more dispersed medium.

2.2. Protein Digestibility

The digestibility of isolated plant-based proteins is being studied to ensure that new protein sources can meet the minimum daily intake of amino acids. The usefulness of plants as a protein source for the human body is limited by the presence of certain compounds that have detrimental physiological effects on protein digestion, thereby limiting their nutritional value [20,21,30].

Protein digestibility is generally determined by the amount of free amino acid groups present in the supernatant of digested samples, provided by the degree of hydrolysis (DH). For pea proteins, values between 60.7% and 80% have been found for concentrated proteins [31,32] and 70.2% to 92% for isolated proteins [31,33]. For soy proteins, values ranging from 73.7% to 97% have been found for concentrated proteins [31,34] and 68% to 97.3% for isolated proteins [31,34,35,36]. For bean proteins, values ranging from 83% to 100% have been found for concentrated proteins [31,37] and 70% to 77.7% for isolated proteins [31,38].

Proteins, whether isolated or concentrated, from different cultivars of the same species can exhibit varying thermal, structural, techno-functional properties and nutritional value, such as amino acid content and digestibility [39]. The different digestibility values found for the same protein can be explained by several factors. The content of globulins is one such factor that can influence this value. Globulins are generally more susceptible to hydrolysis by digestive enzymes [40]. Furthermore, it has been reported that the 7S and 11S fractions of globulins exhibit different in vitro digestibility profiles [41].

Soy and pea proteins exhibited higher digestibility values in the isolated form. This makes sense because, in the isolated form, the degree of purification is higher. Therefore, there are fewer non-protein materials to interfere with digestibility. In concentrated proteins, however, the higher content of fat, carbohydrates, and fibers compared to the isolated form may reduce their digestibility [28,31]. However, there are other more relevant factors that can influence protein digestibility. The use of the appropriate digestive enzyme, processing methods, and, most importantly, the protein structure are the key factors.

Bean proteins exhibited lower digestibility. This can likely be explained by the fact that the molecular structure is globular. Globular proteins tend to be less accessible to digestive enzymes compared to those with a more fibrous structure (more elongated and complex). Alternatively, it could be that bean proteins are more resistant to pH changes. That is, when exposed to acidic pH in the digestive tract, the molecule remains in its most stable conformation, preventing enzymes from reaching the binding sites necessary for hydrolysis. Another possible reason could be the higher presence of antinutritional factors that inhibit enzymes, reducing protein digestibility [35].

2.3. Secondary Structure

The arrangement of amino acids in the polypeptide chain determines their primary, secondary, tertiary, and quaternary structures. In the primary structure, amino acids are linked in a linear sequence. In the secondary structure (Table 2), they form a three-dimensional shape as the main chain begins to branch. In the tertiary structure, the main chain folds. Based on the arrangement of the secondary structure, proteins can be classified into α-helix, β-sheet, β-turn, and random coil [42].

The α-helix occurs when the main chain is coiled around the center of an imaginary rod, with its respective side chains arranged outward, forming a helix [43]. In the β-sheet, the polypeptide chains are arranged linearly and can be paired with each other through hydrogen bonds between their residues [44]. In the β-turn, the main chain folds back on itself, changing direction by up to 180° [45]. The random coil is a conformation in which the chains do not follow a hydrogen bonding pattern, resulting in a disordered three-dimensional arrangement [46].

Table 2. Secondary structure present in isolated and/or concentrated proteins of bean, soybean, and pea.

Variety		α-Helix (%)	β-Sheet (%)	β-Turn (%)	Random Coil (%)	Authors
Black Bean	Isolated protein	7.5 ± 0.0	39 ± 0.0	21.7 ± 0.0	31.8 ± 0.0	[47]
Bambara Bean		15.47 ± 0.52	67.34 ± 2.24	5.6 ± 0.19	11.59 ± 0.38	[48]
Winged Bean		15.38	37.46	31.67	15.38	[49]
Faba Bean		19.7	41.9	12.2	26.2	[50]
Soy	Isolated protein	15.46	46.15	30.78	7.69	[49]
		13	50	22	15	[51]
		18	42	22	18	[52]
	Concentrated protein	18	42	22	18
Pea	Isolated protein	10.43 ± 0.18	24.59 ± 1.13	44.28 ± 0.98	15.66 ±0.84	[53]
	Concentrated protein	21	46	18	15	[52]
		13.91 ± 0.49	53.29 ± 0.72	21.47 ± 0.35	11.33 ± 0.12	[54]

Table 2. Secondary structure present in isolated and/or concentrated proteins of bean, soybean, and pea.

Variety		α-Helix (%)	β-Sheet (%)	β-Turn (%)	Random Coil (%)	Authors
Black Bean	Isolated protein	7.5 ± 0.0	39 ± 0.0	21.7 ± 0.0	31.8 ± 0.0	[47]
Bambara Bean		15.47 ± 0.52	67.34 ± 2.24	5.6 ± 0.19	11.59 ± 0.38	[48]
Winged Bean		15.38	37.46	31.67	15.38	[49]
Faba Bean		19.7	41.9	12.2	26.2	[50]
Soy	Isolated protein	15.46	46.15	30.78	7.69	[49]
		13	50	22	15	[51]
		18	42	22	18	[52]
	Concentrated protein	18	42	22	18
Pea	Isolated protein	10.43 ± 0.18	24.59 ± 1.13	44.28 ± 0.98	15.66 ±0.84	[53]
	Concentrated protein	21	46	18	15	[52]
		13.91 ± 0.49	53.29 ± 0.72	21.47 ± 0.35	11.33 ± 0.12	[54]

2.4. Techno-Functional Properties

Proteins are the primary structural and functional constituents of foods, contributing to biological functions in the body and techno-functional properties in food products. In the food industry, proteins gain functionality through their surface properties, which include the formation and stabilization of emulsions; biological activity (such as enzymatic action); intermolecular interactions; and the ability to influence the sensory properties of foods, such as appearance, aroma, color, texture, water retention, and gel formation [55].

Water retention capacity (WRC) is a property based on the interaction between protein molecules and water. It is measured by the amount of water that one gram of protein powder can absorb. Proteins with high WRC values are commonly used in products such as meats, sausages, cakes, and breads. Oil retention capacity (ORC) is similar to WRC but is determined by the amount of oil that one gram of protein powder can absorb. ORC is widely applied in bakery products, yogurts, and fish-based meat products [56].

Gelling capacity is crucial for products that require elasticity and specific textures for consumer acceptability. This property is commonly utilized in puddings, gelatins, and meat products. Foaming and emulsifying capacities, on the other hand, are determined by the ability of proteins to adsorb at interfaces and bind to air bubbles and oil droplets, respectively. Through these interactions, protein–air or protein–oil complexes form stable films, effectively stabilizing dispersions. Proteins with good foaming capacity are typically used in toppings, cakes, mousses, and meringues, while those with excellent emulsifying capacity are employed in salad dressings and soups [56].

Finally, another important property is the solubility of proteins in solvents, which is studied for applications in both food and beverages. Protein solubility is determined by the proportion of hydrophilic or hydrophobic amino acids present on the exposed surface of the polypeptide chains. It is closely linked to other functional properties. Proteins with high solubility generally exhibit excellent emulsifying, foaming, and gelling capacities due to their good dispersibility and colloidal properties [56].

Table 3. Tecno-functional properties of bean proteins.

Variety		WRC	ORC	EC	ES	LCG	FFC	FS	Authors
Akkus bean (Phaseolus vulgaris)	Isolated protein	190%	410%	468.4 ± 0.8 g·g−1	164.2 ± 12.9 min	90 ± 0 g·L−1	91 ± 1%	65.9%	[57]
Bombay bean (Phaseolus coccineous)		190%	400%	468.5 ± 0.4 g·g−1	62.3 ± 6.0 min	80 ± 0 g·L−1	76 ± 0%	96%
Gembos bean (Phaseolus vulgaris)		180%	540%	435.4 ± 0.6 g·g−1	60.1 ± 1.5 min	100 ± 0 g·L−1	81 ± 2%	81.4%
Hinis bean (Phaseolus vulgaris)		210%	470%	467.8 ± 0.8 g·g−1	60.5 ± 1.1 min	90 ± 0 g·L−1	72 ± 2%	97.2%
Simav bean (Phaseolus vulgaris)		200%	400%	402.7 ± 1.4 g·g−1	135.4 ± 3.8 min	90 ± 0 g·L−1	83 ± 6%	84.3%
White bean (Phaseolus vulgaris)	Isolated protein	189.3 ± 1.9%	300.3 ± 1.5%	68.4 ± 0.6%	96.0 ± 0.4%	ND	50.0%	23.3%	[58]
Faba bean (Vicia faba L.)	Globulins	149.80 ± 0.61%	65.32 ± 0.33%	ND	ND	ND	18.06 ± 2.41%	70.00 ± 8.66%	[59]
	Albumins	ND	229.13 ± 4.42%	ND	ND	ND	133.33 ± 15.73%	39.79 ± 4.09%
Michigan bean (Phaseolus vulgaris L.)	Flour	2.3 g·g−1 **	2.1 g·g−1 **	39.60  ±  0.00%	ND	4.00 ± 0.00%	58.16  ±  0.06%	30%	[60]
	Concentrated protein	4.5g·g−1 **	2.1g·g−1 **	13.33  ±  0.01%	ND	14.00 ± 0.00%	20.06  ±  0.07%	5%
Kidney bean (P. vulgaris L.)	Globulin	2.56 ± 0.06 mL.g−1	1.87 ± 0.06 mL·g−1	ND	95% **	6.00 ± 0.00%	76%	75% **	[61]
	Albumin	3.40 ± 0.10 mL·g−1	2.37 ± 0.12 mL·g−1	ND	48% **	16.00 ± 0.00%	100%	70% **
Mung bean	Isolated protein	1.03 ± 0.09 2.78 ± 0.04 g·g−1	1.00 ± 0.12 3.38 ± 0.12g·g−1	1.77 ± 0.02 3.30 ± 0.05 g.g−1	ND	ND	33.00 ± 2.20 67.50 ± 1.04%	20.00 ± 4.00 56.00 ± 3.98%	[62]
Hyacinth bean (Lablab purpureus)	Isolated protein	321 ± 12.2%	254 ± 0.2%	534 ± 4.5 m2.g−1	2.7 ± 0.1 h	ND	232 ± 12.2 mL·g−1	2.3 ± 0.2 min	[63]

WRC = water retention capacity; ORC = oil retention capacity; EC = emulsifying capacity; ES = emulsion stability; LCG = lowest concentration to form gel; FFC = foam formation capacity; FS = foam stability; ND = not determined. ** Approximate values visually identified from a figure.

presents the values of these properties for different bean varieties, in the form of flour, protein concentrate, or protein isolate.

Pea and soy proteins are the most widely used in the food industry due to their cost, ease of extraction, and well-established and widely studied techno-functional properties. However, these proteins from soy and peas also present poor technological properties, such as low solubility in the common pH range of foods (pH 3–6), as well as limited foam and emulsion formation and stability [64,65]. As a result, the search for new plant protein sources aims to mitigate these technological issues so that food products exhibit sensory properties that are appealing to consumers.

Figure 3 shows a comparison of the techno-functional properties of bean, soy, and pea proteins. The proteins extracted from beans exhibited better values for oil retention capacity (CRO), emulsion capacity (CE), and emulsion stability (EE). The oil retention capacity of proteins is dependent on the surface properties of the molecule, such as area, hydrophobicity, and electrical charge [66]. This highlights that the protein extracted from beans exhibits structural characteristics that favor the interaction of the molecule with oil droplets, keeping them dispersed or retained within its matrix. Thus, bean proteins can be a good option to be used as an emulsifying agent, as moisture and oil retention are desirable characteristics for the mechanical and sensory properties of foods. On the other hand, the proteins extracted from soy and peas exhibit better water retention capacity (WRC), lowest concentration to form gel (LCG), foam formation capacity (FFC), and foam stability (FS) when compared to bean proteins. Soy and pea proteins have a higher fraction of hydrophilic groups, such as amino, carboxyl, hydroxyl, carbonyl, and sulfhydryl, which favors their binding with water. These proteins likely have a higher content of charged and non-polar amino acids sufficient to allow the molecule to unfold more easily at the air–water interface, ensuring a good foaming capacity [67].

3. Strategies for Improving the Techno-Functional and Sensory Characteristics of Bean Protein

Plant-based proteins are widely used in the food and pharmaceutical industries. However, due to their low functionality in their native form, chemical, physical, and biological modifications are performed to improve their properties and, consequently, expand their applications [8].

By “low functionality”, it includes low solubility in aqueous media; sensitivity to changes in pH, temperature, and ionic strength; and the presence of different proteins and fractions that exhibit various isoelectric points, making it of a complex nature [68,69]. In addition, plant proteins also contain specific residues of an antinutritional nature, which are synthesized to protect the plant from insects, viruses, fungi, and other organisms. Modification methods, besides circumventing or reducing these limiting factors, can also be applied to mask undesirable flavors [16].

According to the review by Nasrabadi, Doost, and Mezzenga (2021) [16], protein modification methods can be classified into physical, chemical, biological, and other categories. The physical methods include (i) thermal treatment, (ii) gamma irradiation, (iii) electron beam irradiation, (iv) ultraviolet radiation, (v) pulsed electric field, (vi) high pressure, (vii) sonication, (viii) extrusion, (ix) ball mill treatment, (x) cold atmospheric plasma, and (xi) ultrafiltration. Chemical modification can occur through (xii) glycation, (xiii) phosphorylation, (xiv) acylation, (xv) deamidation, (xvi) and pH change. Biological modification can be (xvii) enzymatic or (xviii) fermentation; it can also be achieved by (xix) complexation and (xx) amyloid fibrillation.

(i)

Mild thermal conditions promote protein unfolding, leading to an intermediate globular state that enhances its functionality. However, under extreme conditions, irreversible changes occur in the molecular structure, promoting denaturation and the aggregation of disulfide, hydrophobic, and electrostatic bonds, resulting in a decrease in its functionality [56].

(ii)

Gamma irradiation causes cross-linking, protein fragmentation, and physical aggregation. The hydroxyl radicals and superoxide anions formed during the process are responsible for altering the primary, secondary, tertiary, and quaternary structures of the proteins [70].

(iii)

Electron beam irradiation is conducted using an electron microscope that employs a heated filament or field emission as an electron source. High-energy irradiated electrons are capable of affecting chemical and molecular bonds in the protein structure, leading to their unfolding and denaturation, resulting in alterations in their functional properties and bioactivity [16].

(iv)

Ultraviolet (UV) light can be absorbed by aromatic amino acids such as tryptophan, tyrosine, and phenylalanine. Therefore, it can be induced that UV irradiation is also capable of chemically modifying the protein structure, and consequently, its techno-functional properties [28].

(v)

Pulsed electric field is a non-thermal method that applies short, repetitive pulses of high voltage to a material placed between two electrodes [71]. This pulse can unfold the protein structure and increase its interaction with the solvent, improving solubility and, consequently, its techno-functional properties [72,73,74].

(vi)

High-pressure treatment acts by breaking electrostatic and hydrophobic interactions and forming new bonds, which can lead to aggregation and, consequently, gelatinization [7,38]. This treatment does not cause significant damage to nutritional value, aroma, color, flavor, or vitamin content, as it only breaks non-covalent bonds in the matrix [75,76,77].

(vii)

Sonication is a process that applies frequencies greater than 20 kHz in an ultrasonic bath, aiming to disperse particles in the medium [78]. It generates regions with mechanical waves under high temperature and pressure, which can induce and accelerate chemical reactions. These reactions, in turn, can modify the secondary structure and partially denature the tertiary and quaternary structures, without significantly altering the primary structure, by breaking non-covalent bonds [48,79,80].

(viii)

Extrusion is a combination of mechanical forces, heat, and pressure that can induce unfolding, denaturation, and aggregation of protein molecules, which enhances their functionality [81].

(ix)

Ball mill treatment is used to reduce particle size in food processing. It is a combination of collision, friction, shear, and heat that can cause changes in the secondary and tertiary structures of proteins [82,83].

(x)

The application of cold atmospheric plasma can induce the breaking of covalent bonds or initiate chemical reactions due to its high energy. It has been used to modify surfaces and biopolymers [84,85,86].

(xi)

Ultrafiltration involves forcing the fluid through the pores of membranes by applying pressure or an electric field. It can alter the protein’s structure and functionality, depending on the membrane pore size, pH, pressure, and the applied electric field [87,88].

(xii)

Glycation occurs through covalent bonds between the amine group of the protein, peptide, or amino acid and the carbonyl group of a reducing sugar, through controlled heating in the presence of water. These conformational changes in the protein structure improve functionality [89,90].

(xiii)

Phosphorylation involves the addition of phosphate groups to the primary sequence of the protein, which alters its functionality by enabling more interactions between protein molecules through phosphorylated regions [91].

(xiv)

Acylation involves the conversion of compounds containing active hydrogens, such as -OH, -SH, and -NH, into esters, thioesters, and amines through the use of acylation reagents [92,93]. This conversion alters the electric charges on the surface of the molecule, which in turn affects its solubility and consequently its functional properties [92,93].

(xv)

Deamidation is a spontaneous, non-enzymatic reaction in which the covalent amide group is converted into a carboxylic acid. This conversion increases the negative charge of the molecule [94,95].

(xvi)

Acidic or alkaline treatments can induce structural and functional changes in proteins. In a basic environment, proteins are denatured and unfolded, exposing hydrophilic groups and sulfhydryl groups within the structure. This exposure promotes increased interaction between molecules [96].

(xvii)

Enzymatic hydrolysis is achieved through the cleavage of peptide bonds using enzymes. Enzymatic cross-linking, on the other hand, despite being classified separately from hydrolysis, is obtained by enzymatic formation of covalent bonds using transglutaminase. This enzyme catalyzes the acyl transfer reaction between the γ-carboxamide group of glutamine bound to the protein and lysine [97].

(xviii)

Fermentation has been employed to enhance the structural, functional, and nutritional properties of plant-based proteins. It has been reported that this method improved the solubility of soy protein, as well as its water and oil retention capacity and foaming ability [98,99].

(xix)

pH-induced complexation facilitates the interaction between plant proteins and polysaccharides, protein–protein, protein–phenolic, or protein–surfactant systems, thereby influencing their techno-functional characteristics. These proteins can electrostatically interact with oppositely charged molecules, forming soluble or insoluble complexes that may alter their properties [70].

(xx)

Amyloid fibrillation involves heating under acidic conditions, leading to protein unfolding and hydrolysis, followed by the one-dimensional arrangement of peptides into a characteristic cross-β pattern [100,101].

Table 4 presents a compilation of modifications applied to bean proteins. Various thermal, physical, chemical, and enzymatic treatments have been widely employed to modify the functional properties of bean proteins and grains, aiming to expand their applications in food products. Recent studies have demonstrated the significant impact of these treatments on parameters such as solubility (S), water holding capacity (WHC), oil holding capacity (OHC), emulsifying capacity (EC) and emulsion stability (ES), foaming capacity (FC), and foam stability (FS).

For instance, Choe et al. (2022) [102] investigated black, common, white, and red beans subjected to boiling in ultrapure water, observing an increase in WHC and the digestibility of starch and proteins, with higher viscosity in black and common beans. However, a reduction in pasting properties was noted, whereas air fryer roasting increased OHC and eliminated pasting properties. For white beans boiled for 50 min, Deb-Choudhury et al. (2021) [103] reported a reduction in globulins, phaseolin, and amino acids such as aspartic acid and arginine. However, they observed an increase in low-molecular-weight isoforms and heat shock proteins (HSPs), highlighting the impact of boiling on the protein profile.

Drying techniques also distinctly influence functional properties. Brishti et al. (2021) [81] compared freeze-drying, spray-drying, and oven-drying for mung beans, demonstrating significant variations in protein morphology and gel characteristics. Freeze-drying promoted porous proteins and elastic gels with good WHC and OHC, while spray-drying resulted in smaller protein particles and wrinkled crystals, exhibiting excellent emulsifying capacity and gel elasticity. Conversely, oven-drying produced compact crystals and aggregated gels, reflecting a reduction in structural flexibility.

Chemical and enzymatic treatments, such as those using bromelain or papain, have also shown effectiveness in modifying protein properties. Xu et al. (2021) [104] reported that enzymatic hydrolysis with bromelain increased hydrophobicity, thereby enhancing WHC and OHC. Similarly, Wani et al. (2015) [105] observed that hydrolysis with papain improved EC, FC, WHC, and OHC, depending on the hydrolysis time. Furthermore, ultrasonic and alkaline treatments have been explored for mung bean proteins. Liu et al. (2022) [82] reported that ultrasound induced structural changes, such as increased β-sheets; higher levels of hydrophobic amino acids; and reduced protein particle size, which resulted in improved antioxidant activity and emulsion stability.

Other studies have focused on specific pH and pressure conditions to alter functional properties. Ahmed et al. (2018) [75] demonstrated that the use of high pressure on kidney bean proteins increased WHC, FC, and EC. Ge et al. (2021) [106] highlighted that the effects of pH vary depending on the protein, with higher EC at pH 7.0 and 9.0, while foam formation was favored in acidic pH. Additionally, chemical modifications such as acylation and succinylation performed on jack bean proteins showed improvements in WHC, EC, and foaming properties, with results dependent on the type of chemical modification [94].

Table 4. Physical, chemical, and biological modifications applied to bean proteins.

Varieties	Treatment	Modifications	References
Beans (black, navy, kidney, and pinto)	Beans boiled in ultrapure water at a ratio of 1:15 (w.v−1) for 90 min	Increase in WRC. Higher viscosity in black and common beans. Increased digestibility of starch and proteins. Decreased paste property.	[103]
	Beans roasted for 20 min in an air fryer at 165 °C	Greater ORC. Loss of paste properties.
Vicilin isolated from kidney bean	95 °C for 15–30 min	Improved S, EC, and FS (at neutral pH), although the FFC decreased. Gradually decreased the levels of total and exposed free sulfhydryls. Gradually increased the hydrophobic surface.	[107]
	95 °C for 60–120 min	From 30 to 60 min, there was no significant change in the free sulfhydryl content. However, after 120 min, the decrease was more pronounced. The hydrophobic surface, EC, FFC, and their stabilities gradually decreased.
White bean	Beans boiled for 50 min	Decreased the amount of globulins, phaseolin, lipoxygenase enzyme, aspartic acid, glutamic acid, arginine, and leucine. Increased the amount of low-molecular-weight isoforms, heat shock proteins (HSPs), tyrosine, lysinoalanine, and methionine.	[104]
Mung bean	Lyophilization: −30°C/48h	Porous protein. Elastic gel with better GC.Good S, WRC, and ORC.	[81]
	Spray dryer: 185 °C inlet and 90 °C outlet	Protein in the form of wrinkled crystals. Elastic gel with better GC. Smaller particle size; good EC and ES. Higher amount of β-sheet.
	Drying in oven: 50 °C/24 h	Protein in the form of compact crystals. Aggregated gel.
Proteins from kidney (P. vulgaris L.), red (P. angularis), and mungo (Phaseolus aureus) beans	95 °C for 30 min	Increased S and CE.	[108]
Faba bean protein	75–175 °C for 60 min	Increased WRC and decreased S.	[109]
Common bean (Phaseolus vulgaris L.)	Boiling for 15 or 120 min	Decreased S. After 120 min, increased WRC and ORC. Decreased EC but increased ES.	[110]
Azuki bean (Vigna angularis)	At 25.0, 32.5, 40.0, 55.0, and 70.0 °C (15–40 min)	The higher the temperature, the greater the water retention capacity (WRC) (g/100 g).	[111]
Cultivars of carioca beans: BRSMG Madrepérola (MA), TAA Dama (DA), BRS Notável (NO), IAC Imperador (IM), TAA Gol (GOL), TAA Bola Cheia (BC)	60 °C/8–12 h	It reduced the S and increased the WRC. It reduced the ORC of the “BC” and “MA” flours but increased it in the “GOL” and “IM” flours.	[112]
	60 °C/8–12 h	The thermal treatment reduced the EC and ES of most flours.
Bambara bean (Vigna subterrânea (L) green)	50 °C, 70 °C, 80 °C, and 100 °C for 10 min	The highest EC was observed at 80 °C at pH 9, and the highest ES was at pH 4. Hydrophobicity decreased between 50 and 80 °C. S decreased at temperatures between 70 and 100 °C.	[48]
Black bean (Vigna cylindrica (L.))	Roasting—180 °C for 20 min; Cooking—Boiling for 30 min; Autoclaving—120 °C for 5 min	Increase in WRC. No significant difference in ORC.	[113]
Proteins from Boer bean, lentil, and chickpea	Bromelain	High hydrophobicity, thus exhibiting WRC and ORC.	[105]
	Alkaline hydrolysis	Good EC, good FFC, and effective inhibitory action on lipid oxidation in emulsions.
Mung bean protein	Ultrasound at 114 W, 222 W, 330 W, 438 W, and 546 W power for 20 min	Increased the content of aromatic and hydrophobic amino acids. Decreased α-helix content and increased β-sheet and β-turn content.	[82]
	Ultrasound at 546 W power for 20 min	Significantly decreased the protein particle size (290.13 nm), exhibited a lower zeta potential (−36.37 mV), and reduced hydrophobic surface (367.95 A.U.), in addition to increasing antioxidant activity.
Mung bean protein	Alkaline treatment	Higher S and free thiol content, smaller particle size, and reduced hydrophobic surface.	[114]
Kidney bean cultivars (P. vulgaris L.)	Papain at a concentration of 0.01 g/10 g of protein isolate for 30 and 60 min	Increased S, WRC, ORC, EC, and ES. The FFC was directly proportional to the hydrolysis time.	[106]
Black bean protein	20 kHz, 150–450 W, 12–24 min	Increase in S.	[48]
Faba bean protein	20 kHz, 50–75% amplitude, 15–30 min	Increase in FFC.	[50]
Kidney bean protein	200–600 MPa, 15 min	Increase in WRC, FFC, and EC.	[75]
Protein isolated from mung bean (MB), black bean (BB), azuki bean (AB), rice bean (RB), kidney bean (KB), speckled kidney bean (SKB), cowpea (CP)	pH 3.0, 5.0, 7.0, and 9.0	All isolates showed lower WRC and ORC at pH 5.0, with no capacity at pH 9.0 due to complete solubility. FFC was lower at pH 5.0 due to reduced S. KB and SKB exhibited the highest foam formation properties. FS was highest at pH 3.0. The highest EC was found at pH 7.0 and 9.0. ES was directly proportional to the increase in pH.	[107]
Jack bean	Acylation using acetic acid and succinic anhydride	Improved WRC. ORC increased with acetylation but decreased with succinylation. Maximum EC was observed at pH 10. ES was higher in the pH range of 4–10. FFC and FS increased with higher protein concentrations.	[95]

WRC = Water Retention Capacity; ORC = Oil Retention Capacity; GC = Gelation Capacity; S = Solubility; EC = Emulsifying Capacity; ES = Emulsion Stability; FFC = Foam Formation Capacity; FS = Foam Stability.

Table 4. Physical, chemical, and biological modifications applied to bean proteins.

Varieties	Treatment	Modifications	References
Beans (black, navy, kidney, and pinto)	Beans boiled in ultrapure water at a ratio of 1:15 (w.v−1) for 90 min	Increase in WRC. Higher viscosity in black and common beans. Increased digestibility of starch and proteins. Decreased paste property.	[103]
	Beans roasted for 20 min in an air fryer at 165 °C	Greater ORC. Loss of paste properties.
Vicilin isolated from kidney bean	95 °C for 15–30 min	Improved S, EC, and FS (at neutral pH), although the FFC decreased. Gradually decreased the levels of total and exposed free sulfhydryls. Gradually increased the hydrophobic surface.	[107]
	95 °C for 60–120 min	From 30 to 60 min, there was no significant change in the free sulfhydryl content. However, after 120 min, the decrease was more pronounced. The hydrophobic surface, EC, FFC, and their stabilities gradually decreased.
White bean	Beans boiled for 50 min	Decreased the amount of globulins, phaseolin, lipoxygenase enzyme, aspartic acid, glutamic acid, arginine, and leucine. Increased the amount of low-molecular-weight isoforms, heat shock proteins (HSPs), tyrosine, lysinoalanine, and methionine.	[104]
Mung bean	Lyophilization: −30°C/48h	Porous protein. Elastic gel with better GC.Good S, WRC, and ORC.	[81]
	Spray dryer: 185 °C inlet and 90 °C outlet	Protein in the form of wrinkled crystals. Elastic gel with better GC. Smaller particle size; good EC and ES. Higher amount of β-sheet.
	Drying in oven: 50 °C/24 h	Protein in the form of compact crystals. Aggregated gel.
Proteins from kidney (P. vulgaris L.), red (P. angularis), and mungo (Phaseolus aureus) beans	95 °C for 30 min	Increased S and CE.	[108]
Faba bean protein	75–175 °C for 60 min	Increased WRC and decreased S.	[109]
Common bean (Phaseolus vulgaris L.)	Boiling for 15 or 120 min	Decreased S. After 120 min, increased WRC and ORC. Decreased EC but increased ES.	[110]
Azuki bean (Vigna angularis)	At 25.0, 32.5, 40.0, 55.0, and 70.0 °C (15–40 min)	The higher the temperature, the greater the water retention capacity (WRC) (g/100 g).	[111]
Cultivars of carioca beans: BRSMG Madrepérola (MA), TAA Dama (DA), BRS Notável (NO), IAC Imperador (IM), TAA Gol (GOL), TAA Bola Cheia (BC)	60 °C/8–12 h	It reduced the S and increased the WRC. It reduced the ORC of the “BC” and “MA” flours but increased it in the “GOL” and “IM” flours.	[112]
	60 °C/8–12 h	The thermal treatment reduced the EC and ES of most flours.
Bambara bean (Vigna subterrânea (L) green)	50 °C, 70 °C, 80 °C, and 100 °C for 10 min	The highest EC was observed at 80 °C at pH 9, and the highest ES was at pH 4. Hydrophobicity decreased between 50 and 80 °C. S decreased at temperatures between 70 and 100 °C.	[48]
Black bean (Vigna cylindrica (L.))	Roasting—180 °C for 20 min; Cooking—Boiling for 30 min; Autoclaving—120 °C for 5 min	Increase in WRC. No significant difference in ORC.	[113]
Proteins from Boer bean, lentil, and chickpea	Bromelain	High hydrophobicity, thus exhibiting WRC and ORC.	[105]
	Alkaline hydrolysis	Good EC, good FFC, and effective inhibitory action on lipid oxidation in emulsions.
Mung bean protein	Ultrasound at 114 W, 222 W, 330 W, 438 W, and 546 W power for 20 min	Increased the content of aromatic and hydrophobic amino acids. Decreased α-helix content and increased β-sheet and β-turn content.	[82]
	Ultrasound at 546 W power for 20 min	Significantly decreased the protein particle size (290.13 nm), exhibited a lower zeta potential (−36.37 mV), and reduced hydrophobic surface (367.95 A.U.), in addition to increasing antioxidant activity.
Mung bean protein	Alkaline treatment	Higher S and free thiol content, smaller particle size, and reduced hydrophobic surface.	[114]
Kidney bean cultivars (P. vulgaris L.)	Papain at a concentration of 0.01 g/10 g of protein isolate for 30 and 60 min	Increased S, WRC, ORC, EC, and ES. The FFC was directly proportional to the hydrolysis time.	[106]
Black bean protein	20 kHz, 150–450 W, 12–24 min	Increase in S.	[48]
Faba bean protein	20 kHz, 50–75% amplitude, 15–30 min	Increase in FFC.	[50]
Kidney bean protein	200–600 MPa, 15 min	Increase in WRC, FFC, and EC.	[75]
Protein isolated from mung bean (MB), black bean (BB), azuki bean (AB), rice bean (RB), kidney bean (KB), speckled kidney bean (SKB), cowpea (CP)	pH 3.0, 5.0, 7.0, and 9.0	All isolates showed lower WRC and ORC at pH 5.0, with no capacity at pH 9.0 due to complete solubility. FFC was lower at pH 5.0 due to reduced S. KB and SKB exhibited the highest foam formation properties. FS was highest at pH 3.0. The highest EC was found at pH 7.0 and 9.0. ES was directly proportional to the increase in pH.	[107]
Jack bean	Acylation using acetic acid and succinic anhydride	Improved WRC. ORC increased with acetylation but decreased with succinylation. Maximum EC was observed at pH 10. ES was higher in the pH range of 4–10. FFC and FS increased with higher protein concentrations.	[95]

WRC = Water Retention Capacity; ORC = Oil Retention Capacity; GC = Gelation Capacity; S = Solubility; EC = Emulsifying Capacity; ES = Emulsion Stability; FFC = Foam Formation Capacity; FS = Foam Stability.

4. Final Considerations

Through this review, it was observed that plant-based proteins do not exhibit good techno-functional properties when used in their native forms. However, when subjected to modifications—whether chemical, physical, or biological—these properties can be enhanced, expanding the potential applications of these proteins in the food industry. Given the vast variety of cultivars, the extensive cultivated areas, and the popularity of beans, this raw material becomes a promising alternative protein source. Despite the color, odor, and flavors, which are often undesirable to consumers, the protein extracted from this legume has a high potential to serve as an ingredient in food matrices, primarily due to its strong emulsifying properties. The modifications applied to bean proteins have proven significant in improving their techno-functional properties.

Among the main challenges to be addressed, the flavor and odor of the protein extracted from beans, the granular texture, low stability during processing and storage, cost, and consumer acceptance stand out. It is believed that optimizing processing methods and developing texturization technologies can improve the sensory profile of these proteins. Therefore, increased investment in studies involving the characterization and improvement of techno-functional and nutritional properties of bean proteins is essential.

Such improvements are of great importance, especially considering the diverse sectors of agro-industries where proteins extracted from beans can be applied. In addition to the food and beverage industry, they can also be used in nutraceuticals and dietary supplements, given their high protein content and balanced amino acid profile; in the pharmaceutical industry, as an ingredient in drug formulations, nutritional supplements, or products for health and wellness; in animal feed, as a protein source to reduce dependence on animal-based proteins; and in the cosmetics industry, due to their moisturizing and nourishing properties for skin and hair.

Unfortunately, the protein extracted from beans is still not widely exploited industrially. This may be due to dietary traditions, as beans are more commonly prepared in traditional forms rather than used as isolated or concentrated protein; the availability of more widely known alternatives such as soy, pea, and lupine; technological challenges, such as the complex protein extraction and purification processes; and the lack of investment in research and development. Despite the growing interest in studying them, there is still a gap in exploring their potential in various food applications and overcoming the challenges associated with their use.